The present invention relates to an airship capable of high-altitude flying and having improved horizontal stability.
FIGS. 5A and 5B show a conventional airship 1. FIG. 5A shows the airship 1 in a condition of flying or staying at a low altitude, and FIG. 5B shows the airship 1 in a condition of flying or staying at a high altitude. The airship 1 has a hull 2, a nose ballonet 5 placed in the bottom of a part of the hull 2 near a nose 3, and a tail ballonet 6 placed in the bottom of a part of the hull 2 near a tail 4. Most part of a space 9 in the hull 2 excluding spaces occupied by the ballonets 5 and 6 is occupied by flotation ballonets filled up with a flotation gas, such as He gas.
The ballonets 5 and 6 are provided with blowers 7 and 8 for taking air into and discharging air from the ballonets 5 and 6, respectively, to vary the mass balance between the nose 3 and the tail 4 selectively to control the pitch angle, i.e., the inclination in a vertical plane, of the airship 1.
Another prior art disclosed in JP-A No. 185894/1990 relates to an airship including a hull filled up with a flotation gas, and provided with a propulsion unit and an attitude control mechanism. This airship is provided with a flotation ballonet filled up with a flotation gas and placed in the hull, which is substantially statically and dynamically symmetrical with respect to an imaginary horizontal plane including the axis of the hull and an imaginary vertical plane including the axis of the hull, a pair of ballonets, i.e., air bags, placed in an upper and a lower part of the hull, respectively, and a pair of ballonets, i.e., air bags, placed in a front and a rear part of the hull, respectively, to improve the maneuverability, to reduce the operating cost and to enhance the weather resistance of the airship. The propulsion unit supplies necessary air into the plurality of ballonets or discharges air from the plurality of ballonets through selector valves, when a control fin included in a tail fin is unable to control the yaw angle and the roll angle satisfactorily while the airship is flying at a low speed or stopping. The attitude of the airship can be stabilized by thus regulating the quantities of air contained in the ballonets to shift the center of gravity of the hull.
The prior arts illustrated by FIGS. 5A and 5B and mentioned in JP-A No. 185894/1990 achieve the control of the pitch by supplying air into or discharging air from the ballonets placed near the nose and the tail, respectively, of the hull to shift the center of gravity along the longitudinal axis of the hull by changing the longitudinal mass balance of the hull. However, since the volumes of the ballonets relative to that of the hull are small, the center of gravity cannot be quickly changed by operating the ballonets and hence the pitch angle cannot be quickly controlled, so that the response of attitude control is not satisfactory.
Since the ballonets are placed in the bottom of the hull in each of those prior art airships, most part of the flotation gas prevails in an upper region of the hull. Therefore, if an upper part of the hull is heated by solar energy, part of the flotation gas prevailing in the upper region of the hull is heated, parts of the flotation gas in different regions of the hull have different specific weights, respectively, and the flotation gas circulates in the hull. Consequently, the front and the rear ballonet are deformed, the mass balance of the airship which has been in a horizontally stabilized state is lost and the hull pitches.
The pitching of the hull caused by a disturbance, such as heating of flotation gas by solar energy, induces the flow of the flotation gas and air in the hull, causing undesirably long displacement of the center of gravity. The displacement of the center of gravity causes change in the attitude of the airship which has been in a horizontally stabilized state. Thus, the prior art airships have poor attitude stability.
It is an object of the present invention to provide an airship having an improved response characteristic for attitude control, and improved attitude stability.
According to the present invention, an airship includes a hull having an axis, bulkheads installed in the hull and dividing the interior space of the hull into a plurality of compartments, a flexible diaphragm provided in each compartment for dividing the compartment into an upper flotation gas containing space and a lower air containing space, and an air supply-and-discharge device placed in the air containing space of each compartment.
In the airship according to the present invention, each bulkhead has an upper part facing the flotation gas containing space of the compartment, and a lower part facing the air containing space of the compartment, and the upper part of each bulkhead is provided with vents through which a flotation gas flows.
In the airship according to the present invention, the lower part of each bulkhead is formed of an airtight sheet.
In the airship according to the present invention, the upper part of each bulkhead is formed of a meshed sheet provided with a plurality of vents.
In the airship according to the present invention, the lower part of each bulkhead is formed of an airtight polymer film.
In the airship according to the present invention, the hull is provided with a plurality of bulkheads dividing the interior space of the hull into compartments, and the number of the compartments is determined such that restoring moment to restore the hull to a horizontal attitude increases with the increase of the hull inclination equal to the angle of the axis of the hull to a horizontal plane and decreases substantially to zero when the hull inclination decreases substantially to zero.
In the airship according to the present invention, the bulkheads installed in the hull divides the interior space of the hull into five compartments.
In the airship according to the present invention, additional bulkheads substantially parallel to the axis are disposed in the compartments, and each additional bulkhead divides the corresponding compartment into a plurality of additional compartments.
In the airship according to the present invention, each of the additional bulkheads has an upper part facing the flotation gas containing space and a lower part facing the air containing space, and the upper part is provided with vents through which the flotation gas flows.
In the airship according to the present invention, the lower part of the additional bulkhead is formed of an airtight sheet.
In the airship according to the present invention, the air supply-and-discharge devices are disposed in the air containing spaces of the additional compartments, respectively.
According to the present invention, the space in the hull is divided axially into the plurality of compartments by the plurality of bulkheads, each compartment is divided into an upper flotation gas containing space and a lower air containing space by the diaphragm, and each bulkhead is provided with the vents that allow the flotation gas to flow between the adjacent upper flotation gas containing spaces. The hull is provided with the air supply-and-discharge devices for supplying external air into the air containing spaces and discharging air from the air containing spaces.
Since the interior space of the hull is divided axially into the plurality of compartments, and each compartment is divided into the lower air containing space and the upper flotation gas containing space, the flotation gas is able to flow freely through the vents between the flotation gas containing spaces in the adjacent compartments even if the airship is operated at a high altitude, such as a stratospheric altitude, is held at a fixed position in an environment where the airship is exposed directly to solar radiation and an upper part of the hull and the flotation gas therein are heated by solar energy. The mass balance can be sharply changed to control the attitude of the airship by controlling the quantities of air contained in the air containing spaces in the axially separated compartments.
According to the present invention, when the interior space of the hull is divided into the plurality of compartments, the number of the compartments is determined such that restoring moment to restore the hull to a horizontal attitude increases with the increase of the hull inclination and decreases substantially to zero when the hull inclination decreases substantially to zero. Therefore, the hull can be surely and quickly restored to a horizontal or substantially horizontal attitude even if the hull is inclined at a large inclination.